Rhetorical, grandiloquent, magniloquent, aureate, flowery, euphuistic, bombastic are comparable when they mean emphasizing style often at the expense of thought.
Rhetorical describes a style, discourse, passage, phrase, or word which, however skillfully constructed or chosen and however effective, impresses the reader or hearer as not natural or effortless, but the result of conscious endeavor to produce an effect.
Grandiloquent implies excess (as of elevation or color) and applies to an exaggerated, high-flown, and often pompous manner or style especially in language.
Magniloquent is not always distinguishable from grandiloquent, but it more often suggests boastfulness or extravagance than a high-flown eloquence.
Aureate implies excessive embellishment of style by strained figures of speech and rhetorical flourishes, strange or high-sounding words, and foreign phrases; in ordinary language and in reference to writings which have no pretensions to literature the same quality is described by flowery .
Euphuistic describes specifically a highly rhetorical and aureate style of the reign of Elizabeth I; in extended use it more often suggests extreme artificiality and a straining after effects that distract attention from the thought, rather than the affectation of elegance and the excessive use of alliteration, antithesis, and similes that characterized the original euphuism and are implied in euphuistic when used in its strict historical sense.
Bombastic implies inflation or grandiosity of style. It suggests verbosity and grandiloquence rather than a straining for rhetorical effects.